3 levels for Doom 2. Based on my old "bhouse" level, but heavily, heavily modified and split into 3 maps.
Motivation: a facility hidden in a cavern has been conducting experiments in hell, and have found a legendary volcano called Erebus. Journey through hell and destroy all that dwell in it.
Credits:
Memfis of Doomworld forums for finding some bugs.
Base:
Modified (bhouse.wad, one of my old wads. Plays and looks completely different though)